Mixed TEHL analysis of tandem hydraulic reciprocating seal in deep-sea hydraulic system considering inter-cavity pressure effect

Connecting two or more seals in series is an effective way to improve the reliability of seals for deep-sea hydraulic systems, but the pressure fluctuations in the inter-cavity between the two-stage seals may have adverse effects on the sealing system. To address it, this paper established a mixed thermo-elastohydrodynamic lubrication (TEHL) model for tandem hydraulic reciprocating seal (HRS) applied in deep-sea hydraulic system. The service state of the seal is defined according to the evolution law of inter-cavity pressure, and the impact of operating conditions on the sealing behavior and performance of the seal under different service status is explored. The research results indicate that tandem seals have a significant advantage over single seals to reduce leakage, but also lead to increased friction in the sealing system. As the inter-cavity pressure increases, the components in the sealing system that mainly perform sealing function gradually change from the main-seal to the sub-seal. It is recommended to reduce the damage to the function of the tandem seal by increasing the volume of the inter-cavity or regularly releasing the inter-cavity pressure, thereby further improving the reliability of the tandem seal in deep-sea hydraulic system.